z80

115 Articles

Protoboard Z80 Computer Teaches The Basics

May 11, 2024 by 16 Comments

As curious people, we’re all incredibly fortunate to live in an age where information can so easily be obtained. If you want to learn how something works, from a cotton gin to an RBMK reactor, you’re just a few keystrokes away from articles, diagrams, and videos on the subject. But as helpful as all of that information can be, we also know that there’s no substitute for hands-on experience.

While we can’t recommend you try building a miniature graphite-moderated nuclear reactor, there’s plenty of other devices that you can study by constructing your own functioning model. For example, when [Jorisclayton] wanted to really know what was going on inside a computer, they decided to go back to basics and build their own Z80 machine. To maximize the experience, they skipped any of the existing kit designs and instead wired the whole thing up by hand across a few perfboards.

The main board contains a 4 MHz Z80 processor, paired with 32K ROM and 64K RAM. Here you’ll also find the clock generator, I/O decoder, serial port, voltage regulator, and a trio of expansion slots that use a long strip of 2.54 mm pin headers as the interface. In the first expansion slot you’ve got a primordial “graphics card” based around the TMS9918 video display controller (VDC) and 16K of additional RAM. The second expansion card has a CompactFlash reader and an LED array mapped to I/O address 0x00h so it can be used for various notifications.

[Jorisclayton] says the final expansion board is still being worked on, but the idea is for it to handle user input through a PS/2 keyboard connector, as well as provide ports for a pair of Super Nintendo (or compatible) controllers. Everything is held together with a minimalist 3D printed frame to show off all that careful soldering.

Obviously there’s no PCB design files to share for this one, but [Jorisclayton] has posted a schematic for wiring everything up if you’re looking for resources to build your own Z80 computer. Sure the chips themselves might no longer be in production, but that doesn’t mean this venerable CPU is going anywhere just yet.

The Z80 Is Dead. Long Live The Free Z80!

April 28, 2024 by 28 Comments

It’s with a tinge of sadness that we and many others reported on the recent move by Zilog to end-of-life the original Z80 8-bit microprocessor. This was the part that gave so many engineers and programmers their first introduction to a computer of their own. Even though now outdated its presence has been a constant over the decades. Zilog will continue to sell a Z80 derivative in the form of their eZ80, but that’s not the only place the core can be found on silicon. [Rejunity] is bringing us an open-source z80 core on real hardware, thanks of course to the TinyTapeout ASIC project. The classic core will occupy two tiles on the upcoming TinyTapeout 7. While perhaps it’s not quite the same as a real 40-pin DIP in your hands, like all of the open-source custom silicon world, it’s as yet early days.

The core in question is derived from the TV80 open-source core, which we would be very interested to compare when fabricated at TinyTapeout’s 130nm process with an original chip from a much larger 1970s process. While It’s true that this project is more of an interesting demonstration of TinyTapeout than a practical everyday Z80, it does at least serve as a reminder that there may be a future point in which a run of open-source real Z80s or other chips might become possible.

This isn’t the first time we’ve featured a TinyTapeout project.

End-Of-Life For Z80 CPU And Peripherals Announced

April 19, 2024 by 57 Comments

In a Product Change Notification (PCN) published on April 15, Zilog (now owned by Littelfuse) announced the End of Life for a range of Z80 products, specifically virtually all of the Z84C00 range. This also includes the peripherals, such as the Z84C10 range of MPUs. These are currently already marked as EoL on stores like Mouser, with Littelfuse noting that the last orders with them can be placed until June 14th of 2024. After that you’ll have to try your luck with shady EBay sellers and a lucky box of old-new-stock found in the back of a warehouse.

What this effectively means is that after just under 48 years since its launch in 1976, the Zilog Z80 will no longer be available for sale as discrete components, which is likely to primarily impact hobbyists and people who are trying to keep retro systems going. This does not mean that it’s the end of the road for Z80, however, as the eZ80 will be produced for the foreseeable future.

These new chips will of course not come in easy to drop in DIPs, making the challenge of breadboarding your own Z80-based microcomputer that much tougher. Yet one thing that definitely won’t happen is any of us witnessing the end of the era of the Z80, 6502 and 8051 architectures.

Thanks to [Techokami] for the tip.

Vintage Particle Counter Is A Treasure Trove Of Classic Parts

April 13, 2024 by 1 Comment

If you need a demonstration of just how far technology has come in the last 40 years, just take a look at this teardown of a 1987 laser particle counter.

Granted, the laser-powered instrument that [Les Wright] scored off of eBay wasn’t exactly aimed at consumers. Rather, this was more likely an instrument installed in cleanrooms to make sure the particulate counts didn’t come out of range. As such, it was built like a battleship in a huge case stuffed with card after card of electronics, along with the attendant pumps and filters needed to draw in samples. But still, the fact that we can put essentially the same functionality into a device that easily fits in the palm of your hand is pretty striking.

[Les] clearly bought this instrument to harvest parts from it, and there’s a ton of other goodness inside, including multiple copies of pretty much every chip from the Z80 family. The analog section has some beautiful Teledyne TP1321 op-amps in TO-99 cans. Everything is in immaculate condition, and obsolete or not, this is an enviable haul of vintage parts, especially the helium-neon laser at its heart, which still works. [Les] promises an in-depth look at that in a follow-up video, but for now, he treats us to a little tour of the optics used to measure particulates by the amount of laser light that’s scattered.

All things considered, [Les] really made out well on this find — much better than his last purchase.

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Revisiting A Z80 Game From 1990

February 8, 2024 by 16 Comments

Back in the days of 8-bit computers, like no doubt many readers of similar age, we wrote little games. First in BASIC, then augmented with little machine code speed-ups. We didn’t come close to [Óscar Toledo Gutiérrez] though, who’s reverse engineering a 2K all-machine-code game he wrote back in 1990. As a tale of software archaeology it’s fascinating.

The game itself is an avoid-the-monsters platformer with plenty of ladders for the little sprite-based protagonist to run down. The computer was a Mexican homebrew educational machine with a TMS9118 display chip and an AY-3-8910 synthesizer, so the result had both color and music. His run through the code breaks it down neatly into individual sections, so it’s possible to see what’s going on without an in-depth knowledge of machine code.

He readily admits it bears all the hallmarks of an 11-year-old’s knowledge at the time, and that it has some parts less elegant, but nevertheless it’s something of an achievement at any age. It was out of date gameplay-wise in 1990 but in 1982 it could probably have been bought on a tape by eager kids. Here in 2024 he’s got it for download should you have a Colecovision or an MSX. There’s a gameplay video below the break, take a look.

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Z80 I/O Madness

January 19, 2024 by 26 Comments

While the 8080 started the personal computer revolution, the Z80 was quickly a winner because it was easier to use and had more capabilities. [Noel] found out though that the Z80 OUT instruction is a little odd and, in fact, some of the period documentation was incorrect.

Many CPUs used memory-mapped I/O, but the 8080 and Z80 had dedicated I/O addressing pins and instructions so you could fill up the memory map with actual memory and still have some I/O devices. A quick look in the famous Zak’s book on Z80 programming indicates that an instruction like OUT (C),A would write the A register to the output device indicated by the BC register pair (even though the instruction only mentions C. However, [Noel] missed the note about the B register and saw in the Zilog documentation that it did. Since he didn’t read the note in the Zak’s book until later, he assumed it was a discrepancy. Therefore, he went to the silicon to get the correct answer.

Breadboarding a little Z80 system allowed him to look at the actual behavior of the instruction. However, he also didn’t appreciate the syntax of the assembly language statements. We’ve done enough Z80 assembly that none of it struck us as particularly crazy, especially since odd instruction mnemonics were the norm in those days.

Still, it was interesting to see him work through all the instructions. He then looks at how Amstrad used or abused the instructions to do something even stranger.

If you want to breadboard a minimal Z80 system, consider this one. If you enjoy abuse of the Z80 I/O system, you don’t want to miss this Z80 hack for “protected mode.”

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